The U-Bahn station Heinrich-Heine-Allee on the Wehrhahn line features three visual and sculptural sound corridors by artist Ralf Brög.
Photograph: Joerg Hempel

“It was an unusual project,” says Berlin-based artist Heike Klussmann, a lead designer of the new U-Bahn line, which opens on Saturday in the German city of Düsseldorf. Fifteen years in the making, the Wehrhahn metro line consists of six new stations running east to west beneath the city centre, collaboratively designed by architects, artists and engineers. “Normally the construction part happens first and then the artists are commissioned. Here the architects, artists and engineers worked together from the beginning,” she says.

It started back in 2001 when a joint proposal by Klussmann and Darmstadt-based architecture practice Netzwerkarchitekten won an EU-wide, two-stage competition to design the stations. They commissioned five artists to develop concepts and, €843m (£657m) and two miles of tunnel boring and excavation later, the results are surprising, outstanding and ambitious.

There have been other art on the underground projects but two factors make this one stand out: the total lack of advertising throughout, and the cohesive vision of a common architectural language.

It’s hard to know where the engineering begins and the art ends

Thomas Stricker

In every station is the “continuum”, an etched concrete skin on all or part of the concourse walls with geometric shapes that expand and contract to create the illusion of three-dimensionality and movement, Klussmann explains. The idea was that there should be two layers to the project: “One layer that connects the stations to one another and another layer that responds to the urban context above ground,” adds Markus Schwieger of Netzwerkarchitekten, who was part of the main coordinating team.

High street-level density means there are no buildings or ticketing facilities above ground; just staircases and escalators taking you down to an expansive space. These entrances were conceived as three-dimensional “incisions” – some have light shafts that let in natural daylight, and all provide dramatic cutaway views down on to the concourse and through to the escalators. “The sightlines up, down and around were all about clarity of orientation and the sort of natural surveillance that you need in an underground system,” says Schwieger.

The station designed by Ralf Brög has three atmospheric sound corridors exploring noise sculpturally and visually, while Ursula Damm’s station features aerial views of Düsseldorf in the entrance. There is also a giant LED wall overlooking the concourse displaying real-time footage of passing pedestrians overlaid with constantly changing geometric structures that respond to the movement of passengers.

At Graf-Adolf-Platz, artist Manuel Franke created an immersive journey where sweeping layers of green rock strata accompany passengers down to the concourse and combine hand-painting with laminated security glass. Klussmann’s graphic black-and-white designs for Pempelforter Straße station play with the architecture and boundaries of the space and traditional notions of perspective to a dazzling effect.

Thomas Stricker conceived Benrather Straße station as a space ship lined with six screens that offer 3D views of planets. The interiors are clad in embossed stainless steel. “This is the ship’s bridge,” says Stricker as we stand in the entrance hall. The feeling of other-worldly travel is enhanced by the station’s angled walls and panoramic windows and the way the stairs widen at the bottom: “It’s hard to know where the engineering begins and the art ends.” Schwieger adds: “We really had to fight with the engineers for these slanted geometries and expanding staircases.”

It was a conscious decision to allow this to be a pure art and architecture experience

Ulla Lux

It may seem surprising that Germany’s first art on the underground project has taken place in this relatively small and well-heeled city by the Rhine – with its population of 600,000 – instead of the larger and edgier metropolises of Berlin, Hamburg or Cologne. Yet Düsseldorf is no slouch in art scene terms. All of the artists selected have links to the city’s Kunstakademie, the renowned art school founded in 1762 whose alumni include Joseph Beuys, Gerhard Richter,Sigmar Polke and Anselm Kiefer. According to Gregor Jansen, director of the Kunsthalle, the city is more interesting than its expensive car and luxury-loving image would have you believe. “It has always been an art city and it still has the most famous art academy in Europe,” he says, referring to the Kunstakademie.

The fall of the Berlin wall saw many galleries, artists, critics and collectors relocate to Berlin but under Düsseldorf’s art-loving mayor, the late Joachim Erwin, things picked up again in the early 90s with the creation of short-lived but influential art shows and and art fairs, says Jansen. Erwin was also the one to give the green light to the new metro line.

A thread of words in hammered steel by artist Enne Haehnle threads its way around Kirchplatz station. Photograph: Joerg Hempel

Currently the city is undergoing a regeneration of sorts, bringing with it both good and bad, says Jansen. A massive flyover that divided the city – but was also much-loved by some urban enthusiasts – has been removed from the city centre and the roads were moved underground. The city’s iconic 1960 Dreischeibenhaus tower block has recently been renovated with no expense spared. A sinuous and angular luxury retail centre by Daniel Libeskind was completed by Hofgarten park in 2013 and a shiny high-end residential and gastro quarter coming up in the old town’s former country courts is creating tension between existing residents and newcomers.

While the 15-year-long building work seems to have riled a number of shopkeepers and residents, the new metro line has been relatively free of major controversy. Yes, some artists wanted to use more expensive materials and the budget prohibited it, but on the other hand, city administrators often didn’t understand the need for a certain material or colour. “Given that there are so many restrictions in public transport construction, every aesthetic and conceptual decision also involved technical decisions,” says Klussmann. “Everybody had to make compromises.”

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The new metro represents a rare moment when people who never usually interact – city bureaucrats, engineers, architects and artists – create something bigger than themselves. As Schwieger says: “Engineers usually work on bridges, they found it exciting to be sitting at the same table as artists and architects.”

With many existing above-ground tram lines that covered the new metro’s route due to be removed, Klussmann believes the city has an opportunity to do something good with the newly acquired public space.

Perhaps surprisingly, the city agreed to the no advertising dimension immediately. Ulla Lux from the city’s cultural department explains their rationale: “It’s so rare to have the opportunity to create an art project of this scale in public space that in the end it was a conscious decision to allow this to be a pure art and architecture experience.”

What is perhaps most inspiring about the project is how the lack of adverts means people can be people, and not consumers. Klussmann says: “Art is often used to attract people to buy things.” But here it is just about the art and the space, and wherever your imagination takes you. How many public spaces can say the same?